System architecture for vacuum processing

ABSTRACT

A system for processing substrates in plasma chambers, such that all substrates transport and loading/unloading operations are performed in atmospheric environment, but processing is performed in vacuum environment. The substrates are transported throughout the system on carriers. The system&#39;s chambers are arranged linearly, such that carriers move from one chamber directly to the next. A conveyor, placed above or below the system&#39;s chambers, returns the carriers to the system&#39;s entry area after processing is completed. Loading and unloading of substrates may be performed at one side of the system, or loading can be done at the entry side and unloading at the exit side.

RELATED APPLICATIONS

This application claims priority benefit from U.S. ProvisionalApplication Ser. No. 61/639,052, filed on Apr. 26, 2012, the entiredisclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

This application relates to systems for vacuum processing, such assystems used in the fabrication of solar cells, flat panel displays,touch screens, etc.

2. Related Art

Various systems are known in the art for fabricating semiconductor IC's,solar cells, touch screens, etc. The processes of these systems areconducted in vacuum and include, e.g., physical vapor deposition (PVD),chemical vapor deposition (CVD), ion implant, etch, etc. There are twobasic approaches for such systems: single-substrate processing or batchprocessing. In single wafer processing, only a single substrate ispresent inside the chamber during processing. In batch processingseveral substrates are present inside the chamber during processing.Single substrate processing enables high level of control of the processinside the chamber and the resulting film or structure fabricated on thesubstrate, but results in a relatively low throughput. Conversely, batchprocessing results in less control over the processing conditions andthe resulting film or structure, but provides a much higher throughput.

Batch processing, such as that employed in systems for fabricating solarcells, touch panels, etc., is generally performed by transporting andfabricating the substrates in a two-dimensional array of n×m substrates.For example, a PECVD system for solar fabrication developed by Roth &Rau utilizes trays of 5×5 wafers for a reported 1200 wafers/hourthroughput in 2005. However, other systems utilize trays having twodimensional arrays of 6×6, 7×7, 8×8, and even higher number of wafers.While throughput is increased utilizing trays of two-dimensional waferarrays, the handling and the loading and unloading operations of suchlarge trays becomes complex.

In some processes, it is required to apply bias, e.g., RF or DCpotential, to the substrate being processed. However, since batch systemutilize a moving tray with the substrates, it is difficult to apply thebias.

Also, while some processes can be performed with the substrate heldhorizontally, some processes can benefit from a vertically heldsubstrate. However, loading and unloading of substrate vertically iscomplex compared to horizontal loading and unloading.

Some processes may require the use of masks to block parts of thesubstrate from the particular fabrication process. For example, masksmay be used for formation of contacts or for edge exclusion to preventshunting of the cell. That is, for cells having contacts on the frontand back sides, materials used for making the contacts may be depositedon the edges of the wafer and shunt the front and back contacts.Therefore, it is advisable to use mask to exclude the edges of the cellduring fabrication of at least the front or back contacts.

As another illustration, for the fabrication of silicon solar cells, itis desirable to deposit blanket metals on the back surface to act aslight reflectors and electrical conductors. The metal is typicallyaluminum, but the blanket metals could be any metal used for multiplereasons, such as cost, conductivity, solderability, etc. The depositedfilm thickness may be very thin, e.g., about 10 nm up to very thick,e.g., 2-3 um. However, it is necessary to prevent the blanket metal fromwrapping around the edge of the silicon wafer, as this will create aresistive connection between the front and back surfaces of the solarcell, i.e., shunting. To prevent this connection, an exclusion zone onthe backside edge of the wafer can be created. The typical dimension ofthe exclusion zone is less than 2 mm wide, but it is preferable to makethe exclusion as thin as possible.

One way to create this exclusion zone is through the use of a mask;however, using masks has many challenges. Due to the highly competitivenature of the solar industry, the mask must be very cheap tomanufacture. Also, due to the high throughputs of solar fabricationequipment (typically 1500-2500 cells per hour), the mask must be quickand easy to use in high volume manufacturing. Also, since the mask isused to prevent film deposition on certain parts of the wafer, it mustbe able to absorb and accommodate deposition build up. Furthermore,since film deposition is done at elevated temperatures, the mask must beable to function properly at elevated temperature, e.g., up to 350° C.,while still accurately maintaining the exclusion zone width, whileaccommodating substrate warpage due to thermal stresses.

SUMMARY

The following summary is included in order to provide a basicunderstanding of some aspects and features of the invention. Thissummary is not an extensive overview of the invention and as such it isnot intended to particularly identify key or critical elements of theinvention or to delineate the scope of the invention. Its sole purposeis to present some concepts of the invention in a simplified form as aprelude to the more detailed description that is presented below.

Embodiments of the invention provide a system architecture that ismodular, in that it enables using different processes and process steps,and versatile, in that it is suitable for fabrication of variousdevices, including, e.g., solar cells, flat panel displays, touchscreens, etc. Moreover, the system can handle different types and sizesof substrates without reconfiguration, but by simply changing thesusceptors used.

The system architecture enables substrate handling, such as loading andunloading in atmospheric environment, separate from the vacuumprocessing. Additionally, various embodiments enable manual loading andunloading with automation in idle or not present, i.e., the system canbe implemented without loading/unloading automation. Inside the vacuumenvironment the system enables static or pass-by processing of thesubstrates. In certain embodiments, vacuum isolation is provided betweeneach processing chamber, using actuated valves. Various embodimentsprovide for electrostatic chucking of the substrates to enable efficientcooling and to prevent accidental movement of the substrates. In otherembodiments, mechanical chucking is enabled using, e.g., spring-loadedclips with relief mechanism for loading/unloading of the substrates.Various embodiments also enable biasing of the substrates using, e.g.,RF or DC bias power, or floating the substrate.

Various embodiments enable simplified handling of substrates by havingthe handling performed on line-array carriers, while processing isperformed on a two-dimensional array of n×m substrates, by processingseveral line-array carriers simultaneously. Other embodiments providefor transport mechanism wherein the substrates are processed in avertical orientation, but loading and unloading is performed while thesubstrates are handled horizontally.

Embodiments of the invention also enables substrate processing usingmasks, which can be implemented by using a dual-mask arrangement. Thetwo part masking system is configured for masking substrates, andincludes an inner mask consisting of a flat metal sheet having aperturesexposing the parts of the wafer that are to be processed; and, an outermask configured for placing over and masking the inner mask, the outermask having an opening cut of size and shape similar to the size andshape of the substrate, the outer mask having thickness larger thanthickness of the inner mask. A mask frame may be configured to supportthe inner and outer masks, such that the outer mask is sandwichedbetween the mask frame and the inner mask. In one example, where thedual-mask arrangement is used for edge isolation, the opening cut in theinner mask is of size slightly smaller than the solar wafer, so thatwhen the inner mask is placed on the wafer it covers peripheral edge ofthe wafer, and the opening cut in the outer mask is slightly larger thanthe opening cut in of the inner mask. A top frame carrier may be used tohold the inner and outer mask and affix the inner and outer masks to thewafer susceptor.

A loading and unloading mechanism is provided, which handles four rowsof substrates simultaneously. The loading/unloading mechanism isconfigured for vertical motion, having a lowered position and anelevated position. In its lowered position, the mechanism is configuredto simultaneously: remove a row of processed substrates from onecarrier, deposit a row of fresh substrates on an empty carrier, deposita row of processed substrates on a substrate removal mechanism, andcollect a row of fresh substrates from a substrates delivery mechanism.The substrate removal mechanism and the substrate delivery mechanism maybe conveyor belts moving in the same or opposite directions. In itselevated position, the mechanism is configured to rotate 180 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, exemplify the embodiments of the presentinvention and, together with the description, serve to explain andillustrate principles of the invention. The drawings are intended toillustrate major features of the exemplary embodiments in a diagrammaticmanner. The drawings are not intended to depict every feature of actualembodiments nor relative dimensions of the depicted elements, and arenot drawn to scale.

FIG. 1 illustrates an embodiment of a multi-substrate processing system,wherein transport carriers support a line-array of substrates, butprocessing is performed on a two-dimensional array of substrates.

FIG. 1A illustrates an example of a system wherein the carriers remainin a horizontal orientation during transport and processing, while FIG.1B illustrates an example wherein the carriers are horizontal duringtransport and loading/unloading, but are vertical during processing.

FIG. 2 illustrates a multi-wafer carrier according to one embodiment,while FIG. 2A illustrates a partial cross-section.

FIG. 2B illustrates an example of carrier for processing silicon wafers,while FIG. 2C illustrates an example of a carrier for processing glasssubstrates.

FIG. 3A is a top view, while FIG. 3B is a side view of a load/unloadmechanism according to one embodiment. FIG. 3C illustrates an embodimentfor substrate alignment mechanism.

FIG. 4 illustrates an embodiment of a vacuum processing chamber 400 thatmay be used with the disclosed system.

FIG. 5 illustrates an embodiment for a mask and carrier assembly.

FIGS. 6A-6C illustrate three embodiments demonstrating how the vacuumchamber can be fitted with different processing sources of varying sizesand configurations.

FIGS. 7A-7E illustrate views of a multi-wafer carrier having anarrangement for dual-mask, according to various embodiments.

FIG. 8 is a cross section of an enlarged part of the frame, outer andinner masks, according to one embodiment, and FIG. 8A is a cross sectionof an enlarged part of the frame, outer and inner masks, according toanther embodiment.

FIG. 9 illustrates an embodiment of the outer mask, with the inner masknested therein.

FIG. 10 illustrates an embodiment of the inner mask for use in edgeisolation.

FIG. 11 illustrate an embodiment of the single wafer carrier.

FIG. 12 illustrate an embodiment of the outer mask, viewing from theunderside.

FIG. 13 illustrates an embodiment of a top frame to support the innerand outer masks.

FIG. 14 illustrates an embodiment of the inner mask for creatingplurality of holes in the wafer.

FIG. 15 illustrates an embodiment of the susceptor for use with the maskof FIG. 9.

DETAILED DESCRIPTION

The following detailed description provides examples that highlightcertain features and aspects of the innovative processing system claimedherein. Various disclosed embodiments provide for a system whereinmultiple substrates, e.g., semiconductor or glass substrates, areprocessed simultaneously inside a vacuum processing chamber, such as,e.g., a plasma processing chamber. While glass substrates, such as thoseused for touchscreens are not generally considered wafers, it should beappreciated that references made to wafers in this disclosure are madefor convenience and ease of understanding, but that glass substrates maybe substituted for all such references.

FIG. 1 is a top-view illustration of an embodiment of a multi-substrateprocessing system, wherein transport carriers support a line-array ofsubstrates, but processing is performed on a two-dimensional array ofsubstrates. In the system 100 illustrated in FIG. 1, the substrates areloaded and unloaded at load/unload station 105, i.e., from the same sideof the system. However, it should be appreciated that the system mayalso be designed such that a loading station is provided on one side ofthe system, while an unloading station is provided on the opposite sideof the system. In some embodiments, loading and/or unloading ofsubstrates onto/from the carriers may be performed manually, while inothers automation is provided to perform one or both of these tasks.

The substrates are loaded onto carriers positioned in load/unloadstation 105, and which were transported from carrier return station 110.Each carrier supports a linear array of substrates, i.e., two or moresubstrates arranged in a single row, in a direction perpendicular to thedirection of travel inside the system. From load/unload station 105 thecarriers are moved via the carrier return station 110 to buffer station115. The carriers are parked in buffer station 115 until the low vacuumloadlock (LVLL) 120 is ready to accept them. In some embodiments, whichwill be described later, the buffer station also serves as the tiltingstation, wherein horizontally oriented carriers are tilted 90° to assumea vertical orientation. In such embodiments, clips are used to hold thesubstrate in place when assuming a vertical orientation.

At the proper time, valve 112 opens and the carriers positioned inbuffer station 115 are transported into LVLL 120. Valve 112 is thenclosed and the LVLL 120 is evacuated to a rough vacuum level. Thereaftervalve 113 opens and the carriers from LVLL 120 are transported into highvacuum loadlock (HVLL) 125. Once HVLL has been pumped to its vacuumlevel, valve 114 opens and the carriers from HVLL 125 are transportedinto processing chamber 130. The system may have any number ofprocessing chambers 130 aligned linearly such that the carriers may betransported from one chamber to the next via a valve positioned betweeneach two processing chambers. At the end of the last processing chamber,a valve is positioned that leads to the reverse loadlock arrangement asin the entrance to the system, i.e., first a HVLL and then a LVLL.Thereafter the carriers exit to the carrier return module 135 via valve116. From return module 135 the carriers are returned to carrier returnstation 110 using, e.g., conveyor positioned above or below theprocessing chambers 130 (not shown).

As noted above, each carrier supports a linear array of substrates,which makes it easier to load and unload the substrates, and makes thecarriers much easier to manufacture, handle, and transport. However, inorder to have high throughput of the system, each processing chamber 130is configured to house and simultaneously process a two-dimensionalarray of substrates positioned on several, i.e., two or more, carrierspositioned one after the other. For better efficiency, in the particularembodiment of FIG. 1, buffer station 115, LVLL 120 and HVLL 125 are eachconfigured to simultaneously house the same number of carrier as aresimultaneously housed inside the processing chamber 130. For example,each carrier may support three glass substrates in one row, but eachprocessing chamber is configured to process two carriers simultaneously,thus processing a two-dimensional array of 3×2 substrates.

According to other embodiments, the load locks and buffer chambers aresized to handle multiple carriers, e.g., two carriers, to provide forincreased pump/vent, and pressure stabilization times. Also, a bufferchamber can be used to transition carrier motion from one of station tostation motion to one of continues pass-by motion inside a processingchamber. For example, if one process chamber process carriers instationary mode while the next chamber processes in pass-by mode, abuffer chamber may be placed between these two chambers. The carriers inthe system create a continuous stream of carriers in the process chamberor module, and each process chamber/module may have 5-10 carrierscontinuously moving in a head to toe fashion past the process source(e.g., heat source, PVD, etch, etc).

As shown in FIG. 1, the parts of the system dedicated for transport,loading and unloading of substrates are positioned in atmosphericenvironment. On the other hand, all processing is performed in vacuumenvironment. Transport, loading and unloading in atmospheric environmentis much easier than in vacuum.

FIG. 1A illustrates an example of a system, such as that shown in FIG.1, wherein the carriers 200 remain in a horizontal orientation duringtransport and processing. The carriers are returned to the startingpoint via conveyor 140 positioned above the processing chambers. Asshown in FIG. 1A, each carrier 200 supports four substrates 220 arrangedlinearly in one row. Also, for explanation purposes, the top part ofchamber 120 is removed, so as to expose the arrangement of six carrierspositioned simultaneously therein. Therefore, according to thisembodiment, while each carrier supports four substrates, each chamberprocess twenty-four substrates simultaneously.

FIG. 1B illustrates an example wherein the carriers are horizontalduring transport and loading/unloading, but are vertical duringprocessing. The arrangement of FIG. 1B is very similar to that of FIG.1A, except that the loadlock and processing chambers are flippedvertically, so as to process the substrates in a vertical orientation.The construction of loadlock and processing chambers in both embodimentsof FIGS. 1A and 1B may be identical, except that in FIG. 1A they aremounted horizontally, while in FIG. 1B they are mounted on their sidevertically. Consequently, the buffer stations 115 and the buffer station145 on the other end of the system, are modified to include a liftingarrangement which changes the orientation of the carriers 90°, as shownin buffer station 145.

FIG. 2 illustrates a line-array carrier according to one embodiment,which may be configured for processing silicon wafers, glass substrates,etc. As shown in FIG. 2, the construction of the line-array carrieraccording to this embodiment is rather simple and inexpensive. It shouldbe appreciated that the carrier can be configured for a different numberof substrates and substrate size, by simply mounting different chucks ontop of the carrier. Also, it should be appreciated that each processingchamber may be configured to accommodate several carrierssimultaneously, thus processing multiple wafers on multiple carrierssimultaneously.

The carrier 200 of FIG. 2 is constructed of a simple frame 205 which isformed by two transport rails 215 and two ceramic bars 210. The ceramicbar 210 improves thermal isolation of the susceptor (not shown) attachedthereto from the remaining parts of the chamber. At least one side ofeach ceramic bar 210 forms a fork arrangement 235 with the transportrail 215, as shown in the callout. A cavity 245 is formed in the forkarrangement 235, such that the ceramic bar 210 is allowed to freely move(illustrated by the double-head arrow) due to thermal expansion, and notimpart pressure on the transport rail 215.

A magnetic drive bar 240 is provided on each of the transport rails 225to enable transporting the carrier throughout the system. The magneticdrive bars ride on magnetized wheels to transport the carrier. Toenhance cleanliness of the system, the drive bars 240 may be nickelplated. This magnetic arrangement enables accurate transport withoutsliding of the carrier due to high accelerations. Also, this magneticarrangement enables large spacing of the wheels, such that the carrieris attached to the wheels by magnetic forces and may cantilever to alarge extent to traverse large gaps. Additionally, this magneticarrangement enables transport of the carrier in either vertical orhorizontal orientation, since the carrier is attached to the wheels bymagnetic forces.

Carrier contact assembly 250 is attached to the transport rail 225 andmates with a chamber contact assembly 252 (see callout) attached to thechamber. The chamber contact assembly has an insulating bar 260 having acontact brush 262 embedded therein. The contact assembly 250 has aconductive extension 251 (FIG. 2A) that is inserted between aninsulating spring 264 and insulting bar 260, thus being pressed againstbrush contact 264 so as to receive bias potential from the matingcontact. The bias may be used for, e.g., substrate bias, substratechucking (for electrostatic chuck), etc. The bias may be RF or DC(continuous or pulsed). The carrier contact assembly 250 may be providedon one or both sides of the carrier.

FIG. 2A is a partial cross-section showing how the carrier istransported and how it receives bias power. Specifically, FIG. 2Aillustrates the drive bar 240 riding on three magnetized wheels 267,which are attached to shaft 268. Shaft 268 extends beyond the chamberwall 269, such that it is rotated from outside the interior vacuumenvironment of the chamber. The shaft 268 is coupled to a motor viaflexible belt such as, e.g., an O-ring, to accommodate variations inshaft diameter.

FIG. 2B illustrates an example of carrier for processing silicon wafers,e.g., for fabricating solar cells. In FIG. 2B wafers 220 may be chuckedto susceptor 223 using, e.g., chucking potential. A lifter 215 may beused to lift and lower the wafers for loading and unloading. FIG. 2Cillustrates an embodiment wherein the carrier may be used for processingglass substrates such as, e.g., touchscreens. In this embodiment thesubstrates may be held in place using mechanical spring-loaded clamps orclips 227. The susceptor 224 may be a simple pallet with arrangement forthe spring-loaded clips.

FIGS. 3A and 3B illustrate an embodiment for substrate loading andunloading mechanism, in conjunction with the carrier return. FIG. 3A isa top view of the load/unload mechanism, while FIG. 3B is a side view.As shown in FIG. 1A, a conveyor returns the carriers after completion ofprocessing. The carriers are then lowered by elevator 107 andtransported horizontally to the loading/unloading station 105. As shownin FIGS. 3A and 3B, a dual conveyor, i.e., conveyors 301 and 303, areused to bring fresh substrates for processing and remove processedwafers. It is rather immaterial which one brings the fresh wafers andwhich one removes the processed wafers, as the system would work exactlythe same regardless. Also, in this embodiment it is shown that conveyors301 and 303 transport substrates in the opposite direction, but the sameresult can be achieved when both conveyors travel in the same direction.

The arrangement of FIGS. 3A and 3B supports handling two carrierssimultaneously. Specifically, in this embodiment processed substratesare unloaded from one carrier, while fresh substrates are loaded ontoanother carrier, simultaneously. Moreover, at the same time, processedsubstrates are deposited on the processed substrate conveyor and freshsubstrates are picked-up from the fresh substrates conveyor, to bedelivered to a carrier in the next round. This operation is performed asfollows.

The substrate pick-up mechanism is configured to have two motions:rotational and vertical motions. Four rows of chucks 307 are attached tothe substrate pick-up mechanism 305. The chucks 307 may be, for example,vacuum chucks, electrostatic chucks, etc. In this specific example, fourrows of Bernoulli chucks are used, i.e., chucks that can hold asubstrate using Bernoulli suction. The four rows of chucks arepositioned two on each side, such that when two rows of chucks arealigned with the carriers, the other two rows are aligned with theconveyors. Thus, when the pick-up mechanism 305 is in its loweredposition, one row of chucks picks up processed substrates from a carrierand another row deposits fresh substrates on another carrier, while onthe other side one row of chucks deposit processed substrates on oneconveyor and another row of chucks pick-up fresh substrate from theother conveyor. The pick-up mechanism 305 then assumes its elevatedposition and rotates 180 degrees, wherein at the same time the carriersmove one pitch, i.e., the carrier with the fresh substrates move onestep, the carrier from which processed substrates were removed movesinto a fresh substrate loading position, and another carrier withprocessed substrates moves into the unloading position. The pick-upmechanism 305 then assumes its lowered position and the process isrepeated.

To provide a concrete example, in the snapshot of FIG. 3A, carrier 311has processed substrates which are being picked-up by one row of chuckson pick-up arrangement 305. Carrier 313 is being loaded with freshsubstrates from another row of chucks of pick-up arrangement 305. On theother side of pick-up arrangement 305 one row of chucks is depositingprocessed substrates on conveyor 303, while another row of chucks ispicking up fresh substrates from conveyor 301. When these actions havebeen completed, pick-up arrangement 305 is raised to its elevatedposition and is rotated 180 degrees, as shown by the curved arrow. Atthe same time, all of the carriers move one step, i.e., carrier 316moves to the position previously occupied by carrier 317, carrier 313,now loaded with fresh substrates, moves to the spot previously occupiedby carrier 316, carrier 311, now empty, moves to the spot previouslyoccupied by carrier 313, and carrier 318, loaded with processedsubstrates moves into the spot previously occupied with carrier 311. Nowthe pick-up arrangement is lowered, such that carrier 311 is loaded withfresh substrates, processed substrates are removed from carrier 318, thesubstrates removed from carrier 311 are deposited onto conveyor 303, andfresh substrates are picked-up from conveyor 301. The pick-uparrangement 305 is then elevated, and the process repeats.

The embodiment of FIGS. 3A and 3B also utilizes an optional mask lifterarrangement 321. In this embodiment, masks are used to generate arequired pattern on the surface of the substrate, i.e., expose certainareas of the substrate for processing, while covering other areas toprevent processing. The carrier travels through the system with the maskplaced on top of the substrate until it reaches the mask lifer 321. Whena carrier with processed substrates reaches the mask lifter (in FIGS. 3Aand 3B, carrier 318), the mask lifter 321 assumes its elevated positionand lifts the mask from the carrier. The carrier can then proceed to theunload station to unload its processed substrates. At the same time, acarrier with fresh substrates (in FIG. 3B carrier 319), movers into themask lifter arrangement and mask lifter 321 assumes its lowered positionso as to place the mask onto the fresh substrates for processing.

As can be appreciated, in the embodiment of FIGS. 3A and 3B, the masklifter removes the masks from one carrier and places them on a differentcarrier. That is, the mask is not returned to the carrier from which itwas removed, but is rather placed on a different carrier. Depending onthe design and number of carriers in the system, it is possible thatafter several rounds a mask would be returned to the same carrier, butonly after being lifted from another carrier. The converse is also true,i.e., depending on the design and the number of carriers and masks inservice, it is possible that each mask would be used by all carriers inthe system. That is, each carrier in the system would be used with eachof the masks in the system, wherein at each cycle of processing throughthe system the carrier would use a different mask.

As shown in the callout, the carrier elevator may be implemented byhaving two vertical conveyor arrangements, one on each side of thecarriers. Each conveyor arrangement is made of one or more conveyor belt333, which is motivated by rollers 336. Lift pins 331 are attached tothe belt 333, such that as the belt 333 moves, the pins 331 engage thecarrier and move the carrier in the vertical direction (i.e., up ordown, depending on which side of the system the elevator is positionedat and whether the carrier return conveyor is positioned over or belowthe processing chambers).

FIG. 3C illustrates an embodiment for substrate alignment mechanism.According to this embodiment, chuck 345 has spring loaded alignment pins329 on one side and a notch 312 on the opposite side. A rotatingpush-pin 341 is configured to enter the notch 312 to push the substrate320 against the alignment pin 329 and then retract, as illustrated bythe dotted-line and rotational arrow. Notably, the rotating push-pin 341is not part of the chuck 345 or the carrier and does not travel withinthe system, but is stationary. Also, the spring-loaded alignment pin iscompressed to a lower position if a mask is used. Thus, a substratealignment mechanism is provided which comprises a chuck having a firstside configured with an alignment pin, a second side orthogonal to thefirst side and configured with two alignment pins, a third side oppositethe first side and configured with a first notch, and a fourth sideopposite the second side and configured with a second notch; thealignment mechanism further comprising a first push-pin configured toenter the first notch to push the substrate against the first alignmentpin, and a second push-pin configured to enter the second notch and pushthe substrate against the two alignment pins.

FIG. 4 illustrates an embodiment of a vacuum processing chamber 400 thatmay be used with the disclosed system. In the illustration of FIG. 4,the lid of the chamber is removed to expose its internal construction.The chamber 400 may be installed in a horizontal or verticalorientation, without any modifications to its constituents or itsconstruction. The chamber is constructed of a simple box frame withopenings 422 for vacuum pumping. An entry opening 412 is cut in onesidewall, while an exit opening 413 is cut in the opposite sidewall, toenable the carrier 424 to enter the chamber, traverse the entirechamber, and exit the chamber from the other side. Gate valves areprovided at each opening 412 and 413, although for clarity in theillustration of FIG. 4 only gate valve 414 is shown.

To enable efficient and accurate transport of the carrier 424 in ahorizontal and vertical orientation, magnetic wheels 402 are provided onthe opposing sidewall of the chamber. The carrier has magnetic bars thatride on the magnetic wheels 402. The shafts upon which the wheels 402are mounted extend outside the chamber into an atmospheric environment,wherein they are motivated by motor 401. Specifically, several motors401 are provided, each motivating several shafts using belts, e.g.,O-rings. Also, idler wheels 404 are provided to confine the carrierslaterally.

A feature of the embodiment of FIG. 4 is that the diameter of themagnetic wheels is smaller than the chamber's sidewall thickness. Thisenables placing magnetic wheels inside the inlet and outlet openings 412and 413, as shown by wheels 406 and 407. Placing wheels 406 and 407inside the inlet and outlet opening 412 and 413 enables smoothertransfer of the carriers into and out of the chamber, as it minimizesthe gap that the carriers have to traverse without support from wheels.

FIG. 5 illustrates an embodiment for a mask and carrier assembly.Progressing from left to right along the curved arrow, asingle-substrate mask assembly 501 is mounted onto a mask carrier 503,supporting several mask assemblies; and the mask carrier 503 is mountedonto a substrate carrier 505. In one embodiment, springs between thefloating mask assemblies 501 keep them in place for engagement withguide pins 507, provided on the substrate carriers 505, such that eachmask is aligned to its respective substrate. Each single-substrate maskassembly is constructed of an inner foil mask that is cheap and capableof many repeated uses. The foil mask is made of s flat sheet of magneticmaterial with perforations according to a desired design. An outer maskcovers and protects the inner mask by taking the heat load, so that thefoil mask does not distort. An aperture in the outer mask exposes thearea of the inner mask having the perforations. A frame holds the innerand outer masks onto the mask carrier 503. Magnets embedded in thesubstrate carrier 505 pull the inner foil mask into contact withsubstrate.

Each substrate support, e.g., mechanical or electrostatic chuck, 517supports a single substrate. The individual chucks 517 can be changed tosupport different types and/or sizes of substrates, such that the samesystem can be used to process different sizes and types of substrates.In this embodiment the chuck 517 has substrate alignment pins 519 whichare retractable, and provisions to align the substrate on top of thechuck. In this embodiment, the provisions to enable alignment consist ofa slit 512 accommodating a retractable pin that pushes the substrateagainst alignment pins 519 and then retracts out of the slit 512. Thisallows for aligning the substrate and the mask to the substrate carrier,such that the mask is aligned to the substrate.

As can be understood, the system described thus far is inexpensive tomanufacture and provide efficient vacuum processing of varioussubstrates, such as, e.g., solar cells, touchscreens, etc. The systemcan be configured with double or single end loading and unloading, i.e.,substrate loading and unloading from one side, or loading from one sideand unloading from the opposite side. No substrate handling is performedin vacuum. The system is modular, in that as many vacuum processingchambers as needed may be installed between the input and outputloadlocks. The vacuum chambers have a simple design with few parts invacuum. The vacuum chambers may be installed in a horizontal or verticalorientation. For example, for solar cell processing the system mayprocess the substrates in a horizontal orientation, while fortouchscreens the substrates may be processed in a vertical orientation.Regardless, loading, unloading and transport in atmospheric environmentis done with the substrates in a horizontal orientation. The processingsources, e.g., sputtering sources, may be installed above and/or belowthe substrates. The system is capable of pass-by or static processes,i.e., with the substrate stationary or moving during vacuum processing.The chambers may accommodate sputtering sources, heaters, implant beamsources, ion etch sources, etc.

For solar applications the vacuum chamber may include a low energyimplanter (e.g., less than 15 KV). For specific solar cell design, suchas PERC, IBC or SE, the mask arrangement may be used to perform maskedimplant. Also, texture etch may be performed with or without mask, usingan ion etch source or laser assisted etch. For point contact cells,masks with many holes aligned to the contacts can be used. Also, thickmetal layers can be formed by serially aligning several PVD chambers andforming layers one over the other serially.

For touch panel applications, the chambers may be used to deposit coldand/or hot ITO layers using PVD sources. The processing is performedwith several, e.g., three touch panels arranged widthwise on eachcarrier, and several, e.g., two, carriers positioned inside each chambersimultaneously for higher throughput but simpler handling. The samesystem can handle touchscreens for pads or cellphone size glass withoutany internal reconfigurations. Simply, the appropriate carrier isconfigured and the entire system remains the same. Again, no substratehandling is performed in vacuum.

The handling and processing operations can be the same for all types andsizes of substrates. An empty carrier moves to load from carrier returnelevator. If a mask is used, the mask is removed and stays at theelevator. Substrates are loaded onto the carrier in atmosphericenvironment. The carrier moves back to the elevator and the masks areplaced on top of the substrates. The carrier then moves into the loadlock. In vacuum the carrier transport is via simple magnetic wheelspositioned in chamber wall and energized from outside the chamber inatmospheric or vacuum environment. The chambers can have valves forisolation, and can have sources above or in a drawer for process belowthe substrates. The substrates can be removed at an unload end of thesystem, or left on carriers to return to the loading end, i.e., entryside of the system. Carriers return on simple conveyor belt from processend of the system to load end of the system. Simple pin conveyor liftsor lowers the carriers to or from load and unload stations.

FIGS. 6A-6C illustrate three embodiments demonstrating how the vacuumchamber can be fitted with different processing sources of varying sizesand configurations. In the examples of FIGS. 6A-6C it is assumed thatthe substrates are arrange three-wide, but of course more or lesssubstrates can be arranged on a carrier widthwise. Also, in FIGS. 6A-6Cit is assumed that the processing chamber can accommodate severalcarriers, e.g., two or three, for simultaneous processing. The sourcesillustrated in FIGS. 6A-6C may be any processing sources, such as, e.g.,PVD, etch, implant, etc.

FIG. 6A illustrates an embodiment wherein a single source 601 isprovided on chamber 600. This single source is used to process all ofthe substrates positioned inside the chamber 600. The source 601 mayhave length and/or width that covers all of the substratessimultaneously. For some sources, it may be too complicated or tooexpensive to fabricate a single source with such a large size. Forexample, if source 601 is a sputtering source, the target must be madevery large, which is expensive, complicated, and leads tounder-utilization. Therefore, according to the embodiments of FIGS. 6Band 6C several smaller sources are used. In the embodiment of FIG. 6Beach of the sources 603A-603C is wide enough to cover only a singlesubstrate, but it may cover more than one substrate lengthwise, i.e., inthe direction of substrate travel. By staggering the sources such thateach source covers only one of the substrate in each carrier, all of thesubstrates can be processed. Such an arrangement is particularlysuitable for pass-by processing. Conversely, in the embodiment of FIG.6C each of the sources 606A-606C is wide enough to cover all of thesubstrates in one carrier, i.e., in a direction perpendicular to thesubstrate travel direction, but is too narrow to cover all of thesubstrates positioned within the chamber. In fact, in some embodimentseach of the sources 606A-606C is even narrower than one substrate. Suchan arrangement is equally suitable for pass-by or static processing.

The embodiments described above provide for a vacuum processing chamberhaving a vacuum housing sized for housing and processing severalsubstrate carriers simultaneously. The housing is also configured forsupporting several processing sources simultaneously. The processingsources may be, e.g., sputtering sources, which may be narrow sourceshaving length sufficient to traverse all substrates held by a substratecarrier, but may be narrower than the width of a substrate positioned onthe carrier. Several such sources may be positioned back-to-back overthe entire or part of the length of the chamber in the travel directionof the carrier. The chamber has several shafts positioned on twoopposing sides to transport the carriers inside the chamber. Each shaftis rotated by a flexible belt that is motivated by a motor. Each shafthas several magnetic wheels positioned thereupon in alternating poleorder, i.e., while one wheel may have its outside circumferencemagnetized south and inside diameter magnetized north, the neighboringwheel would have its outer circumference magnetized north and insidediameter magnetized south. The chamber also has an entry sidewall havingan inlet opening and an exit sidewall opposite the entry sidewall andhaving an outlet opening; wherein a magnetized wheel arrangement ispositioned inside the entry sidewall and protruding into the inletopening and having a magnetized wheel arrangement positioned inside theexit sidewall and protruding into the outlet opening, so as to drive thesubstrate carriers passing through the inlet and outlet openings.

The disclosed system is a linear system wherein the chambers arearranged linearly, one chamber coupled to the next, such that substratecarriers enter the system from one side, traverse all the chambers in alinear fashion, and exit the system on the opposite side. The carriersmove from one chamber directly to the next via valve gates separatingthe chambers. Once a carrier exits the vacuum environment of the system,it enters an elevator and is moved vertically to a return conveyor,which transport the carrier horizontally back to the entry side of thesystem, wherein it enters another elevator and is moved vertically to beloaded with fresh substrates and enter the vacuum environment of thesystem again. While the carrier is transported in atmosphericenvironment it is held in a horizontal orientation. However, in oneembodiment, when the carrier enters the vacuum environment it is rotatedto a vertical orientation, such that the substrates are processed whileheld in a vertical orientation.

The system may have a loading and unloading station positioned at theentry side of the system. The loading and unloading system has arotating structure upon which four rows of chucks are positioned, tworows on each side of the rotation axis. On each side of the rotationaxis one row of chucks is configured for unloading processed substratesand one row of chucks is configured for loading fresh substrates. Therotating structure is configured for vertical motions, wherein when itassumes its lower position the structure picks-up substrates and when itassumes its elevated position the structure rotates 180 degrees. Also,when the structure is in its lowered position, on each side of therotation axis one row of chucks picks-up substrates while the other rowof chucks deposits, i.e., releases, its substrates. In one embodiment,two conveyors are provided across the entry to the system, wherein oneconveyor delivers fresh substrates while the other conveyor removesprocessed substrates. The rotating structure is configures such that inits lower position one row of chucks is aligned with the conveyordelivering fresh substrates while the other row of chucks is alignedwith the conveyor removing processed substrates. Simultaneously, on theother side of the rotation axis, one row of chucks is aligned with anempty carrier while the other row of chucks is aligned with a carrierholding processed substrates.

In some embodiments provisions are made to apply potential to thesubstrates. Specifically, each carrier includes a conductive strip that,when the carrier enters a processing chamber, is inserted into a slidingcontact comprising an elongated contact brush and a conformal insulatingspring that is configured to press the conductive strip against theelongated contact brush. An insulating strip, such as a Kapton strip,can be used to attach the conductive strip to the carrier.

When processing of the substrates requires the use of masks, the masksmay be placed individually on top of each substrate, or one mask may beformed to cover all substrates of one carrier simultaneously. The maskmay be held in place using, e.g., magnets. However, for accurateprocessing the mask must be made very thin, and consequently may deformdue to thermal stresses during processing. Additionally, a thin mask maycollect deposits rapidly and the deposits may interfere with theaccurate placing and masking of the mask. Therefore, it would beadvantageous to use the dual-mask arrangement according to theembodiments disclosed below.

FIGS. 7A-7E illustrate views of a multi-wafer carrier having anarrangement for dual-mask, according to various embodiments. FIG. 7Aillustrates a multi-wafer carrier with dual-masks arrangement, whereinthe mask arrangement is in the lower position such that the inner maskis in intimate physical contact with the wafer; FIG. 7B illustrates amulti-wafer carrier with dual-masks arrangement, wherein the maskarrangement is in the elevated position thereby enabling replacement ofthe wafers; FIG. 7C illustrates a multi-wafer carrier with dual-masksarrangement, wherein wafer lifters are included for loading/unloadingwafers; FIG. 7D illustrates a partial cross-section of a multi-wafercarrier with dual-masks arrangement, wherein the mask arrangement andthe wafer lifters are in the elevated position; and FIG. 7E illustratesa partial cross-section of a multi-wafer carrier with dual-masksarrangement, wherein the mask arrangement and the wafer lifter are inthe lower position.

Referring to FIG. 7A, the multi-wafer carrier, also referred to ascarrier support 700 has three separate single-wafer carriers orsusceptors 705, which are supported by a susceptor frame or bars 710,made of, e.g., ceramic. Each single-wafer carrier 705 is configured forholding a single wafer together with a dual-mask arrangement. In FIG. 7Athe dual-mask arrangement is in a lowered position, but no wafer issituated in any of the carriers, so as to expose the carriers'construction. In FIG. 7B the dual-mask arrangement is shown in thelifted position, again without wafers in any of the carriers. In theembodiments of FIGS. 7A-7E a lifter 715 is used to lift and lower thedual-mask arrangement; however, for lower cost and less complication,lifter 715 may be eliminated and the dual-mask arrangement may be liftedmanually. Transport rails 725 are provided on each side of the frames710, to enable transporting the carrier 700 throughout the system.

Each of single-wafer carriers 705 has a base 730 (visible in FIG. 7B),which has a raised frame 732 with a recess 735 to support a wafersuspended by its periphery. The base 730 with the frame 732 form apocket 740 below the suspended wafer, which is beneficial for capturingbroken wafer pieces. In some embodiments, the frame 732 is separablefrom the base 730. Outer mask 745 is configured to be mounted on theframe 732, so as to cover the frame 732 and cover the periphery of theinner mask, but expose the central part of the inner mask whichcorresponds to the wafer. This is exemplified by the cross-sectionillustration in the embodiment of FIG. 8.

In FIG. 8, base or susceptor 805 has raised frame 830 with recess 832,which supports wafer 820 at its periphery. The base 805 with frame 830forms pocket 840, and the wafer is suspended above the pocket. A seriesof magnets 834 are positioned inside the raised frame 830, so as tosurround the periphery of the wafer 820. In some embodiments, especiallyfor high temperature operations, the magnets 834 may be made of SamariumCobalt (SmCo). Inner mask 850 is positioned on top of the raised frame830 and the wafer 820, and is held in place by magnets 834, such that itphysically contacts the wafer. Outer mask 845 is placed over andphysically contacts the inner mask 850, such that it covers theperiphery of the inner mask 850, except for the area of the inner masksthat is designed for imparting the process to the wafer. An example ofouter mask 945 is shown in FIG. 9, in this example made of a foldedsheet of aluminum, wherein the inner mask is covered by the outer mask,except for a small peripheral edge 952, since the example is for an edgeshunt isolation processing. An example of the inner mask 750 for edgeshunt isolation is illustrated in FIG. 10, which is basically a flatsheet of metal having an aperture of size and shape as that of thewafer, except that it is slightly smaller, e.g., 1-2 mm smaller than thesize of the wafer. In the embodiment of FIG. 8, mask frame 836 isprovided to enable supporting and lifting of the inner and outer maskoff of the carrier. In such a configuration, the outer mask issandwiched between the mask frame 836 and the inner mask 850.

FIG. 8A illustrates another embodiment, which may be used, for example,for forming contact patterns on the back of a wafer. In this embodiment,the susceptor forms a top platform to support the wafer on its entiresurface. Magnets 834 are embedded over the entire area of the susceptorbelow the top surface of the susceptor. The inner mask 850 covers theentire surface of the wafer 820 and has plurality of holes according tothe contact design.

Turning back to FIGS. 7A-7E, lifter 715 can be used to raise the outermask, together with the inner mask. Also, wafer lifter 752 can be usedto lift the wafer off of the frame 730, so that it could be replacedwith a fresh wafer for processing, using a robot arm. However, lifters715 and 752 can be eliminated and the operations of lifting the masksand replacing the wafer may be done manually instead.

In the embodiments described above with reference to FIG. 8, the carriersupports the wafer on its peripheral edge, such that the wafer issuspended. The pocket formed below the wafer traps broken wafer piecesand prevents wraparound of deposited material. On the other hand, in theembodiment of FIG. 8A the wafer is supported over its entire surface.The mask assembly is lowered in place for sputter or other form ofprocessing, and is lifted, manually or mechanically, for loading andunloading of wafers. A series of magnets on the carrier help secure theinner mask in place and in tight contact with the wafer. After repeateduses, the outer and inner masks can be replaced, while the rest of thecarrier assembly can be reused. The frame 810, also referred to as maskassembly side bars, may be made from low thermal expansion material,such as Alumina or Titanium.

According to the above embodiments, the inner mask establishes anintimate gap free contact with the substrate. The outer mask protectsthe inner mask, the carrier and the frame from deposited material. Inthe embodiments illustrated, the outer and inner mask openings are in apseudo-square shape, suitable for applications to mono-crystalline solarcells during edge shunt isolation process. During other processes theinner mask has a certain apertures arrangement, while the outer mask hasthe pseudo-square shaped aperture. Pseudo-square shape is a square withits corners cut according to a circular ingot from which the wafer wascut. Of course, if poly-crystalline square wafers are used, the outerand inner mask openings would be square as well.

FIG. 11 illustrate an embodiment of the single wafer carrier 1105. Thewafer rests at its periphery on recess 1132. Magnets 1134, shown inbroken line, are provided inside the carrier all around the wafer.Alignment pins 1160 are used to align the outer mask to the carrier1105. An embodiment of the outer mask is shown in FIG. 12, viewing fromthe underside. The outer mask 1245 has alignment holes or recesses 1262corresponding to the alignment pins 1260 of the carrier 1205.

FIG. 13 illustrates an embodiment of a top frame 1336 used to hold theouter and inner masks and secure the masks to the susceptor. The topframe 1336 may be made by, e.g., two longitudinal bars 1362, heldtogether by two traverse bars 1364. The outer mask is held inside pocket1366. Alignment holes 1368 are provided to align the top frame to thesusceptor.

FIG. 14 illustrates an example of an inner mask with a hole-patterndesigned, for example, for fabricating plurality of contacts on thewafer. Such an inner mask can be used with the susceptor shown in FIG.15, wherein the magnets 1534 are distributed over the entire area belowthe surface of the wafer. The magnets are oriented in alternatingpolarization.

An upper or outer mask may be made from thin, e.g., about 0.03″,aluminum, steel or other similar material, and is configured to matewith a substrate carrier. An inner mask is made from a very thin, e.g.,about 0.001 to 0.003″, flat steel sheet, or other magnetic materials,and is configured to be nested within the outer mask.

According to further embodiments, arrangement for supporting wafersduring processing is provided, comprising: a wafer carrier or susceptorhaving a raised frame, the raised frame having a recess for supporting awafer around periphery of the wafer and confining the wafer topredetermined position; an inner mask configured for placing on top ofthe raised frame, the inner mask having an aperture arrangementconfigured to mask part of the wafer and expose remaining part of thewafer; and an outer mask configured for placing over the raised frame ontop of the inner mask, the outer mask having a single opening configuredto partially cover the inner mask. A top frame carrier may be used tohold the inner and outer mask and affix the inner and outer masks to thewafer susceptor.

Magnets are located in the susceptor and alternate N-S-N-S-N completelyaround the frame or completely below the entire surface of the susceptorand directly under the wafer. The outer and inner masks are designed tobe held to the frame by magnetic forces only, so as to enable easy andfast loading and unloading of substrates.

The mask assembly is removable from the wafer carrier and support frameto load the substrate into the carrier. Both the outer and inner masksare lifted as part of the mask assembly. Once the wafer is located onthe carrier in the wafer pocket, the mask assembly is lowered back downonto the carrier. The inner mask overlaps the top surface of the wafer.The magnets in the carrier frame pull the inner mask down into intimatecontact with the substrate. This forms a tight compliant seal on theedge of the wafer. The outer mask is designed in order to preventdeposition on the thin compliant inner mask. As explained above, thedeposition process might cause the inner mask to heat, causing the maskto warp and loose contact with the wafer. If the mask looses contactwith the wafer the metal film will deposit in the exclusion zone on thesurface of the substrate wafer. The pocket and friction force created bythe magnets keep the substrate and mask from moving relative to eachother during transport and deposition, and the outer mask prevents filmdeposition on the inner mask and prevents the inner mask from warping.

The mask assembly can be periodically removed from the system with thecarrier by use of a vacuum carrier exchange. The carrier exchange is aportable vacuum enclosure with carrier transport mechanism. It allowsthe carriers to be exchanged “on the fly” without stopping thecontinuous operation of the system.

While this invention has been discussed in terms of exemplaryembodiments of specific materials, and specific steps, it should beunderstood by those skilled in the art that variations of these specificexamples may be made and/or used and that such structures and methodswill follow from the understanding imparted by the practices describedand illustrated as well as the discussions of operations as tofacilitate modifications that may be made without departing from thescope of the invention defined by the appended claims.

1. A system for processing substrates in vacuum chamber, comprising: aplurality of carriers, each carrier configured for supporting andtransporting substrates throughout the system; a loading station forloading substrates onto the carriers; a carrier transport system fortransporting the carriers throughout the system and returning thecarriers to the loading station; a loadlock chamber arrangement forintroducing carries into vacuum environment; and, at least one vacuumprocessing chamber receiving a plurality of carriers from the loadlockarrangement, the vacuum processing chamber sized and configured forsimultaneously housing the plurality of carriers and simultaneouslyprocessing substrates positioned on the plurality of carriers.
 2. Thesystem of claim 1, wherein each of the carries is configured forsupporting a linear array of 1×n substrates, wherein n is an integerlarger than 1, such that the vacuum processing chamber simultaneouslyhouses and processes an array of m×n substrates, wherein m is the numberof carriers housed within the vacuum processing chamber and wherein m isan integer larger than
 1. 3. The system of claim 1, further comprising abuffer station positioned between the loading station and the loadlockarrangement, the buffer station configured to simultaneously house atleast the same number of carriers as are simultaneously housed in theprocessing chamber.
 4. The system of claim 3, wherein the buffer stationcomprises carrier rotating arrangement for rotating the carriers from ahorizontal orientation to a vertical orientation.
 5. The system of claim4, wherein the carrier transport arrangement transports the carriers inhorizontal orientation in atmospheric environment and in a verticalorientation in vacuum environment.
 6. The system of claim 1, wherein thecarrier transport system comprises a conveyor for returning carriers tothe loading station after completion of processing.
 7. The system ofclaim 6, wherein the conveyor passes above the processing chamber inatmospheric environment.
 8. The system of claim 6, wherein the carriertransport system further comprises a plurality of magnetic wheelsarrangement and each of the carriers comprises magnetic bars that rideon the magnetic wheels.
 9. The system of claim 8, wherein the pluralityof magnetic wheels arrangement comprises a plurality of rotating shaft,each of the rotating shafts having a plurality of magnetic wheelsattached thereto in alternating magnetic polarity.
 10. The system ofclaim 9, wherein each of the shafts it rotated by a flexible belt. 11.The system of claim 10, wherein the flexible belt comprises an o-ring.12. The system of claim 8, wherein the vacuum processing chamber has aninlet opening and an outlet opening, and wherein some of the magneticwheels are positioned within the inlet and outlet openings.
 13. Thesystem of claim 1, wherein the carrier transport system comprises afirst carrier elevator coupled to the loading station and a secondcarrier elevator coupled to end of the system opposite the loadingstation.
 14. The system of claim 1, further comprising a substratepick-up arrangement having a plurality of rows of chucks, each chuckconfigured for holding a substrate, the substrate pick-up arrangementconfigured to move up and down vertically and to rotate about an axis,the substrate pick-up arrangement further configured to simultaneouslyremove processed substrates from one carrier and load fresh substrateson another carrier.
 15. The system of claim 14, wherein the substratepick-up arrangement is configured to simultaneously deposit processedsubstrates on one conveyor and pick-up fresh substrates from anotherconveyor, at the same time that the pick-up arrangement simultaneouslyremoves the processed substrates from one carrier and load freshsubstrates on another carrier.
 16. The system of claim 15, wherein theplurality of chucks comprises plurality of Bernoulli chucks which areconfigured to hold substrates using Bernoulli suction.
 17. The system ofclaim 15, wherein the pick-up arrangement has two rows of chucks on oneside of the axis and two rows of chucks on the other side of the axis.18. The system of claim 14, wherein the transport arrangement isconfigured to move the carriers one step each time the pick-uparrangement rotates 180 degrees.
 19. The system of claim 14, furthercomprising a mask lifter arrangement having a mask lifter configured toremove masks from carriers with processed substrates and place the maskson different carriers with fresh substrates.
 20. The system of claim 1,further comprising a plurality of masks and a mask lifter for liftingthe masks from the carriers for substrate loading and unloading.
 21. Thesystem of claim 1, further comprising a plurality of mask assemblies,each mask assembly comprising an inner mask, an outer mask and a maskframe coupling the inner mask and outer mask to one of the carriers. 22.The system of claim 1, further comprising a substrate alignmentmechanism which comprises: a chuck having a first side configured withan alignment pin, a second side orthogonal to the first side andconfigured with two alignment pins, a third side opposite the first sideand configured with a first notch, and a fourth side opposite the secondside and configured with a second notch; and, a first push-pinconfigured to enter the first notch to push the substrate against thefirst alignment pin, and a second push-pin configured to enter thesecond notch and push the substrate against the two alignment pins.